The invention set forth in this specification pertains to new and improved infrared thermometers and more specifically to infrared thermometers which utilize light from a collimated light source, preferably a laser, for targeting purposes so that the infrared thermometer will be used at a specific, desired distance from an area.
It is considered that an understanding of the invention will be facilitated by an explanation of certain of the terms used in referring to the present invention. The term "infrared thermometer" used in this specification is a comparatively recent English term or expression which is commonly utilized to designate an apparatus which determines temperature by measuring the infrared radiation given off from a specific area such as, for example, at a specific area along a surface, within a container or the like.
It is considered that it is well established that it is desirable to construct such infrared thermometers utilizing a housing containing an infrared radiation detector, appropriate electronics for indicating temperature in accordance with the radiation received by such a detector and a reflector structure for use in transmitting the radiation emitted from a specific area where the temperature measurement is being made to the infrared detector. Normally a hood is located generally around the reflector structure and the infrared detector so as to exclude ambient radiation from reaching the infrared detector.
Normally the reflector structure utilized reasonably corresponds to reflector structures such as are commonly employed in various types of telescopes. For the purposes of the present invention it it considered to be relatively immaterial as to whether or not the reflector structure is of a Cassegrainian, a Newtonian, a Gregorian or a Coude focus type or of a modification of any of these. It is considered relatively undesirable to utilize a prime focus type of reflector structure for reasons which are relatively unimportant to an understanding of this invention.
All of these types of reflector structures can be constructed so as to be focused at infinity. This is considered desirable when an instrument is to be used in taking temperature measurements of an area at a significant distance from an infrared thermometer. All of these types of reflector structures can also be constructed to be focused at a comparatively small area or spot at a specific distance from an infrared thermometer. Such a comparatively small area or spot may be referred to as a focal point of the optical structure. It is considered, however, that it is better practice to refer to such a comparatively small area or point as the principal focus of the reflector structure since such a reflector structure may not be as accurate as desired from an optical standpoint and, hence, may not accurately focus on a theoretical type focal point. Such a principal focus may be defined as the smallest area from which radiation can be transmitted using a reflector structure as herein indicated.
The construction of an infrared thermometer so that the reflector structure used with it has such a principal focus is considered to be quite desirable in many applications of infrared thermometers. Frequently the users of such devices will desire to determine the precise temperature of a specific, frequently small part in a relatively inaccessible location such as, for example, a specific small bearing within a large gear box. A problem in making a temperature measurement at such a precise location with a known infrared thermometer concerns the relative difficulty involved in locating the infrared thermometer so that the area where the temperature measurement is to be made is located precisely at the principal focus of the reflector structure used. Such precise placement is necessary in order to ensure the accuracy of any temperature measurement made.
Such precise placement in effect involves two different factors: (1) alignment of the infrared thermometer "optics" or reflective system with the target area involved in making the temperature measurement; and (2) precise control of the distance of the thermometer from the target area. Although the matter of securing a precise desired position of an infrared thermometer can be handled by the use of conventional "tools" such as a graduated scale, or a range finder, or the like, and a sighting scope or the like, the use of such expedients is not considered desirable. Frequently an individual utilizing an infrared thermometer finds it very inconvenient to take the time to separately utilize two different locating "expedients" as indicated. Frequently time considerations such as are involved in making a temperature measurement on a moving part which is only visible for a comparatively short period preclude the use of such time consuming positioning expedients.